Chapter 13 PWMWord格式.docx

Chapter 13 PWMWord格式.docx

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centeralignedoutputmodeandfouravailableclocksources.ThePWMmodulehaseightchannelswithindependentcontrolofleftandcenteralignedoutputsoneachchannel.

Eachoftheeightchannelshasaprogrammableperiodanddutycycleaswellasadedicatedcounter.Aflexibleclockselectschemeallowsatotaloffourdifferentclocksourcestobeusedwiththecounters.Eachofthemodulatorscancreateindependentcontinuouswaveformswithsoftware-selectabledutyratesfrom0%to100%.ThePWMoutputscanbeprogrammedasleftalignedoutputsorcenteralignedoutputs.

13.1.1Features

周期和占空比双缓冲

在有效周期的末尾或通道被禁用，更改才会有效（PWM计数器归零）

8个8位或4个16位PWM通道

Fourclocksources（A,B,SA,andSB）provideforawiderangeoffrequencies

4个时钟源（A，B，SA和SB）提供了广泛的频率

紧急关闭

ThePWMblockincludesthesedistinctivefeatures:

•EightindependentPWMchannelswithprogrammableperiodanddutycycle

•DedicatedcounterforeachPWMchannel

•ProgrammablePWMenable/disableforeachchannel

•SoftwareselectionofPWMdutypulsepolarityforeachchannel

•Periodanddutycyclearedoublebuffered.Changetakeseffectwhentheendoftheeffectiveperiodisreached（PWMcounterreacheszero）orwhenthechannelisdisabled.

•Programmablecenterorleftalignedoutputsonindividualchannels

•Eight8-bitchannelorfour16-bitchannelPWMresolution

•Fourclocksources（A,B,SA,andSB）provideforawiderangeoffrequencies

•Programmableclockselectlogic

•Emergencyshutdown

13.1.2运行模式

可编程禁止时钟进入分频器，以进入低功耗的等待模式。

Freeze模式中有一个软件可编程选项禁止时钟输入分频器。

这对仿真是有益的

Thereisasoftwareprogrammableoptionforlowpowerconsumptioninwaitmodethatdisablestheinputclocktotheprescaler.

Infreezemodethereisasoftwareprogrammableoptiontodisabletheinputclocktotheprescaler.Thisisusefulforemulation.

13.2外部信号描述13.2ExternalSignalDescription

ThePWMmodulehasatotalof8externalpins.该PWM模块共有8外部引脚。

13.2.1PWM7—PWMChannel7

ThispinservesaswaveformoutputofPWMchannel7andPWM通道7作为输入的紧急关断功能

ThispinservesaswaveformoutputofPWMchannel7andasaninputfortheemergencyshutdownfeature.

13.2.2PWM6—PWMChannel6

ThispinservesaswaveformoutputofPWMchannel6.

13.2.3PWM5—PWMChannel5

ThispinservesaswaveformoutputofPWMchannel5.

13.2.4PWM4—PWMChannel4

ThispinservesaswaveformoutputofPWMchannel4.

13.2.5PWM3—PWMChannel3

ThispinservesaswaveformoutputofPWMchannel3.

13.2.6PWM3—PWMChannel2

ThispinservesaswaveformoutputofPWMchannel2.

13.2.7PWM3—PWMChannel1

ThispinservesaswaveformoutputofPWMchannel1.

13.2.8PWM3—PWMChannel0

ThispinservesaswaveformoutputofPWMchannel0.

寄存器中的保留位总是为0

13.3.2RegisterDescriptions

13.3.2.1PWMEnableRegister（PWME）

EachPWMchannelhasanenablebit（PWMEx）tostartitswaveformoutput.WhenanyofthePWMExbitsareset（PWMEx=1）,theassociatedPWMoutputisenabledimmediately.However,theactualPWMwaveformisnotavailableontheassociatedPWMoutputuntilitsclocksourcebeginsitsnextcycleduetothesynchronizationofPWMExandtheclocksource.

NOTE

ThefirstPWMcycleafterenablingthechannelcanbeirregular.Anexceptiontothisiswhenchannelsareconcatenated.Onceconcatenatedmodeisenabled（CONxxbitssetinPWMCTLregister）,enabling/disablingthecorresponding16-bitPWMchanneliscontrolledbytheloworderPWMExbit.Inthiscase,thehighorderbytesPWMExbitshavenoeffectandtheircorrespondingPWMoutputlinesaredisabled.Whileinrunmode,ifalleightPWMchannelsaredisabled（PWME7–0=0）,theprescalercountershutsoffforpowersavings.

1=通道x使能.下一个时钟开始输出PWM

0=通道x禁止

当在16位模式时，使能控制由1；

3；

5；

7位决定。

在16位模式时0，2，4，6位将没有用。

在运行过程中，如果8个通道被关掉，那么预分频记数器也将关掉，为了省电。

PWMEPWME_PWME0-----》PWME_PWME7

IfCON67=1,thenbithasnoeffectandPWMoutputline6isdisabled.

IfCON45=1,thenbithasnoeffectandPWMoutputbit4isdisabled

IfCON23=1,thenbithasnoeffectandPWMoutputbit2isdisabled.

IfCON01=1,thenbithasnoeffectandPWMoutputline0isdisabled.

PWME7:

PulseWidthChannel7Enable

0Pulsewidthchannel7isdisabled.

1Pulsewidthchannel7isenabled.ThepulsemodulatedsignalbecomesavailableatPWMoutputbit7whenitsclocksourcebeginsitsnextcycle.

PWME6:

PulseWidthChannel6Enable

0Pulsewidthchannel6isdisabled.

1Pulsewidthchannel6isenabled.ThepulsemodulatedsignalbecomesavailableatPWMoutputbit6whenitsclocksourcebeginsitsnextcycle.IfCON67=1,thenbithasnoeffectandPWMoutputline6isdisabled.

PWME5: